emulate usb keyboard and potentiometer + multi keyboard shortcut

I need emulate usb keyboard , for make an usb controller for live music on Android Tablet usb OTG,

I need slider potentiometer that emulate arrows left/right movement

I need buttons that emulate multi keyboard shortcut like alt + F1 alt+F2 ......

I need slider that emulate cursor scrollling left/right

Which model of Arduino is suitable?

exist an example freeware source code?

regards

Old post, but as I'm somewhat in to keyboards I'll reply:

Ema2019:
Which model of Arduino is suitable?

Any Arduino with 32U4 chip will do the job.

Ema2019:
exist an example freeware source code?

Yes, in Arduino IDE> Examples>USB>Keyboard/Mouse

There is plenty examples how to do that in Youtube.
Practically any buttons, sliders, potentiometers/rotary encoders will do the job.